From nobody Mon Feb 9 16:53:01 2026 Received: from out-178.mta1.migadu.com (out-178.mta1.migadu.com [95.215.58.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 34F6C38F943 for ; Thu, 5 Feb 2026 09:02:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.178 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770282141; cv=none; b=tPP/fBaYX8zcQnj+JLFxJm7LSOBM73Q0VlyQqX7IV9CDqoeYWBkklcmOutX6ROucPQORZfrZzN3QEu9lsnCfGoTFdv5zp/GPJRjNrRavYbKZpgnNptd09/pjifKGlsozx/SaTFsBMm/Sym2dAvvaOyvLFQ2YR+kwVSqbqlCzUeo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770282141; c=relaxed/simple; bh=IWoGrVhRudg5G8dt0ysljDnISQHoFtUlDKI74tS99zE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qpljrEN/gLNbAhrXjMb0VrP1mokIBIv65oD/PWvTBQ4dh+ARxgKZUF3b2q5XmcnrleZI2UGnD1QTt8FwZhenMF6fyDsZwl1ia84NWrLl8k1YpAgE2eGf/WYR3WDdBgdg6qNK28atc44347BHABzeSj84P1ErtKlHrA6mW8G0C/Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=Dk4DPTIq; arc=none smtp.client-ip=95.215.58.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="Dk4DPTIq" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1770282129; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Gok/w53D1QZxQSSXx2OlMZE8/juZC59RiuuDAMJ7kJY=; b=Dk4DPTIqYdy81yvOV5kdlf416talo3dyPs0MfQaXzaDe5ybLplNcdp4FZV8tB1P+UZyQUj ofUyTY0uPInDGvWXqBQh63gIq+LsUrDcU7Z5JdphaFdyiOUbjxlvmCc/PJTtdYWzKTxqZ/ HFwMLiIP7udwzuEPcKdmwPec7LxuiI8= From: Qi Zheng To: hannes@cmpxchg.org, hughd@google.com, mhocko@suse.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, harry.yoo@oracle.com, yosry.ahmed@linux.dev, imran.f.khan@oracle.com, kamalesh.babulal@oracle.com, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, chenridong@huaweicloud.com, mkoutny@suse.com, akpm@linux-foundation.org, hamzamahfooz@linux.microsoft.com, apais@linux.microsoft.com, lance.yang@linux.dev, bhe@redhat.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, Muchun Song , Qi Zheng Subject: [PATCH v4 08/31] mm: memcontrol: prevent memory cgroup release in get_mem_cgroup_from_folio() Date: Thu, 5 Feb 2026 17:01:27 +0800 Message-ID: In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" From: Muchun Song In the near future, a folio will no longer pin its corresponding memory cgroup. To ensure safety, it will only be appropriate to hold the rcu read lock or acquire a reference to the memory cgroup returned by folio_memcg(), thereby preventing it from being released. In the current patch, the rcu read lock is employed to safeguard against the release of the memory cgroup in get_mem_cgroup_from_folio(). This serves as a preparatory measure for the reparenting of the LRU pages. Signed-off-by: Muchun Song Signed-off-by: Qi Zheng Reviewed-by: Harry Yoo Acked-by: Shakeel Butt --- mm/memcontrol.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index ac75e48f144c1..9e7b00f1450e7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -991,14 +991,18 @@ struct mem_cgroup *get_mem_cgroup_from_current(void) */ struct mem_cgroup *get_mem_cgroup_from_folio(struct folio *folio) { - struct mem_cgroup *memcg =3D folio_memcg(folio); + struct mem_cgroup *memcg; =20 if (mem_cgroup_disabled()) return NULL; =20 + if (!folio_memcg_charged(folio)) + return root_mem_cgroup; + rcu_read_lock(); - if (!memcg || WARN_ON_ONCE(!css_tryget(&memcg->css))) - memcg =3D root_mem_cgroup; + do { + memcg =3D folio_memcg(folio); + } while (unlikely(!css_tryget(&memcg->css))); rcu_read_unlock(); return memcg; } --=20 2.20.1